The muscle location looks more like a palace/castle/theatre type place. It doesn't look like your typical gym or pose down location. There is a beautiful tapestry and big ornate white pillars.

Could this be 1/2 of the detour and then the Legoland puzzle is the other one and Jeremy and Sandy had to give up on the Legos?

I don't think the Legos can be part of the Detour because then they will have nothing in Belgium except the Pitstop. Why fly somewhere for that? Doing an ARI at Legoland makes sense because the airport is literally in their backyard.